Tuesday, February 26, 2013

Let's Talk About Gluten. Please. This Has Gotten A Little Out of Control

You certainly don't have to look very hard to find articles and blog posts on gluten and its purported association with a variety of health issues such as obesity, heart disease, arthritis, and non-celiac gluten sensitivity. While I don't really doubt that some people without celiac disease might legitimately be affected by gluten, I think the discussion around gluten and it's non-celiac ill effects have now crossed the line into fad. Wheat Belly, a diet book authored by cardiologist William Davis, is currently the #2 best selling health and fitness book on Amazon, which advocates eliminating wheat entirely from our diets, whole grain or not, largely based upon the premise that modern wheat is nothing like what our grandparents used to eat, and so it must be connected to these growing problems, much less the increased prevalence of celiac disease. Big Ag, essentially, has manipulated the genes of this staple beyond recognition, and the unintended consequences are vast and dire, amounting to "the most powerful disruptive factor in the health of modern humans than any other". While I haven't read the book, I'm familiar with a lot of the arguments it makes, and how they are perceived in the general public, especially the contention that Davis is referring to GMO wheat, which does not exist on the market. Unfortunately it's pretty difficult to find a good, genuine science-based take on it. To paraphrase Keith Kloor, the majority of what you'll find only has the veneer of science.

When I was in high school, and as an undergrad in the humanities, writing a research paper meant I started with a thesis statement and found evidence to support whatever it was I wanted to advocate for. In science-based medicine, you test a hypothesis by conducting a randomized control trial if possible, and ultimately by finding all available published reports and presenting the entire story (systematic review), or by combining the statistical analysis of multiple studies into a single large study (meta-analysis). This is not a subtle difference. Wheat Belly is a prime example of the former, which is not necessarily a bad thing, per se. People can make a compelling argument without a systematic review, but it is not acceptable as a last word in medicine, health, or nutrition, period. While there may be evidence to support the idea, it's easy to minimize or even completely overlook evidence to the contrary, especially since you're not really making a point to look for it. It seems pretty obvious that the discussion around wheat could use a little objectivity.

Take a look at this pretty balanced article recently published by the New York Times on the increasing diagnoses of celiac disease.

BLAME for the increase of celiac disease sometimes falls on gluten-rich, modern wheat varietals; increased consumption of wheat, and the ubiquity of gluten in processed foods.

Yet the epidemiology of celiac disease doesn’t always support this idea. One comparative study involving some 5,500 subjects yielded a prevalence of roughly one in 100 among Finnish children, but using the same diagnostic methods, just one in 500 among their Russian counterparts.

Differing wheat consumption patterns can’t explain this disparity. If anything, Russians consume more wheat than Finns, and of similar varieties.

Neither can genetics. Although now bisected by the Finno-Russian border, Karelia, as the study region is known, was historically a single province. The two study populations are culturally, linguistically and genetically related. The predisposing gene variants are similarly prevalent in both groups.

The article goes on to suggest that exposure to different microbial environments is the biggest factor, but it's rather apparent that we have can't just point to a simple answer. The world is a complex place, our bodies are complex, nutrition and health are complex. This is pretty much what you'd expect, right?

Now take a look at some of the massivecoverage on the recent randomized control trial showing significant cardiovascular benefits to the Mediterranean diet. Here's a good analysis from The Harvard School of Public Health. The Mediterranean diet arm of the study were encouraged to liberally use olive oil, eat seafood, nuts, vegetables, and whole grains, including a specific recommendation that pasta could be dressed with sofrito (garlic, tomato, onions, and aromatic herbs). The control diet this ended up favorably compared to was quite similar, but specifically geared toward being low-fat. Both were discouraged from eating red meat, high-fat dairy products like cream and butter, commercially-produced bakery goods, and carbonated beverages.

The largest differences between the two diets centered around discouraging vegetable oils, including olive oil, and encouraging 3 or more pasta or starchy dishes per day in the control group. To me, this suggests that Wheat Belly lives in that sweet spot for widespread dissemination of being easily actionable, having some evidence to support it so that you get some good anecdotes and positive results, but is vastly oversimplified and not suitable or necessary for everyone. Remember, the Wheat Belly diet implicates even organic whole grains as being irredeemably manipulated. It's a completely wheat free diet, because modern wheat is the greatest negative factor in human health. Based on an actual experiment of almost 7,500 people, we have strong evidence that it's the amount of wheat people eat that is problematic. You can eat some whole grains daily and still vastly decrease your risk of heart disease and obesity as long as you don't eat them 3 or more times a day.

The appendix to the NEJM study indicates that some of the patients in the control diet complained about bloating and fullness, but nothing similar from the Mediterranean diet group. The implications seem fairly obvious: there is little basis to make a draconian decision to completely eliminate something with proven health benefits such as whole grains from your diet unless you genuinely suffer from celiac disease. If you're interested in losing weight, think maybe you have gluten sensitivity, or just want to eat healthier, try something like this diet first, and definitely don't put your gluten free diet pamphlets in my child's take-home folder at school. That wasn't cool.

Update: Take a look at this critical post about the RCT of the Mediterranean diet. There's some perspective on the magnitude of the effect they found, and some compliance issues with the recommended diets that I'm not convinced are as damning as he suggests. I also find this sentence a bit odd:

So while you might be less likely to have a heart attack or stroke, you're no less likely to die. This is why I'm so confused they ended the study early.

I don't know. I'd rather just not have a heart attack or stroke. Nevertheless, it's a thoughtful and overall very thorough take on the study.

Yeah, thank you for pointing that out. I've heard that was the argument. Unfortunately, there's little to no basis that the genetic alteration of wheat in and of itself is meaningful at all. It's more of an ideological red herring, based upon very low levels of evidence that has limited value.

Let me put it this way: If I could go into PubMed, search "William Davis wheat" and find a systematic review of dozens of epidemiological studies in a peer-reviewed publication, I'd respect his approach in taking his findings into a book for popular consumption. Seeing as he went straight to the book with no pretense of systematically looking at anything, and got it published by Rodale, it's pretty easy to be skeptical.

One thing is for sure, a lot of processed junk food is made with endosperm and not whole grains, and has sugar added. If people reduce these in their diet, it's not surprising that they'd lose some weight. It's great if you want to advocate people do this, and to inspire them to live healthier lives. It's great if you want to question the old conventional wisdom of a low-fat diet, but in order to really do it you can't cherry pick your way to that conclusion, much less say all wheat, organic, whole, durum, whatever, is essentially a chronic poison. Or to say that whole grains are analogous to filtered cigarettes. That's quackery, plain and simple.

You're right that there is considerably more autoimmunity in Finns to gluten, according to that one study. The strains/amount of wheat consumed nor genetics appear to make any difference. That's the difference between writing a term-paper and a systematic review. You have to accept that these types of results are out there, and they don't fit in the narrative.